However, Miliband will hold out the prospect of an in/out referendum if a new EU treaty transferred more powers from national to EU level as part of a 'referendum lock' bill.

"It is unlikely there will be any such proposals for a transfer of powers in the next parliament, but the British people must know that the history of the EU – as well as uncertainty about precisely what a changing Europe and further integration in the eurozone might involve – means a further transfer of power remains possible," he will say.

"The next Labour government will legislate for a new lock – there would be no transfer of powers from the UK to the EU without a referendum on our continued membership of the EU," Miliband adds.

With two months to go until the European elections, at which the anti-EU Ukip party is expected to make a strong showing, Labour is anxious to avoid the charge that it is the anti-referendum party. Opinion polls indicate that an 'in/out' referendum would be too close to call.

However, business leaders have expressed fears that the uncertainty over the UK's future in the 28-country bloc could make the country less attractive for businesses.

Labour's new position is similar to that of the Liberal Democrats, regarded by most as being the most pro-European UK party.

In January 2013 Prime minister David Cameron announced plans to re-negotiate the UK's EU membership terms followed by a referendum in 2017 if his Conservative party wins next year's general election. The Conservative party has also attempted to push through legislation guaranteeing a plebiscite by 2017 only for the bill to be rejected in January by Labour and Liberal Democrat members of the House of Lords.

Although German chancellor Angela Merkel has expressed support for re-opening the EU treaties to deepen the integration of the eighteen eurozone countries, there is little appetite in most capitals for a fresh round of treaty change just four years after the Lisbon treaty came into force.

In an article in the Financial Times, also published on Wednesday, Miliband stated that, if re-elected, Cameron's government "would be dominated by an all-consuming and damaging obsession within his party about whether Britain should leave the EU.

Cameron, for his part, tweeted that "by his own admission, Ed Miliband says it's unlikely there'll be an in/out referendum on Europe under Labour."

"Only the Conservative Party can guarantee and deliver that in/out referendum," he added.